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Regex Tester

Test regular expressions with real-time match highlighting. Browse 15+ pre-built patterns for common use cases.

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//g
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What is Regex Tester?

StackPro's Free Regex Tester is a developer-focused tool for building, testing, and debugging regular expressions with real-time match highlighting. Paste your test string, write a regex pattern, and instantly see all matches highlighted with detailed match information including groups and indices. The Pattern Library tab provides 15+ pre-built, tested regex patterns for common tasks like email validation, URL matching, phone numbers, dates, IP addresses, and more — click to load into the tester instantly.

How to Use Regex Tester

  1. Enter your regular expression pattern in the regex input field.
  2. Toggle flags (global, case-insensitive, multiline, etc.) as needed.
  3. Paste or type your test string in the textarea below.
  4. View real-time match highlights and match details in the results panel.
  5. Use the Pattern Library tab to browse and load pre-built regex patterns.

Features

  • Real-time match highlighting as you type
  • Flag toggles: global, case-insensitive, multiline, dotAll, unicode
  • Detailed match panel with groups, indices, and capture info
  • Find-and-replace testing with capture group references
  • Pattern Library with 15+ pre-built tested patterns
  • Quick reference sidebar with regex cheatsheet
  • Pattern history (last 20 tests)
  • Permalink generator for sharing patterns

Frequently Asked Questions

What is the Pattern Library?▼
The Pattern Library contains 15+ pre-built, tested regular expressions for common use cases like email validation, URLs, phone numbers, dates, IP addresses, and more. Each pattern includes a description, the regex, flags, and example matches. Click "Use this" to instantly load any pattern into the tester.
What regex flavors are supported?▼
The tester uses JavaScript's built-in RegExp engine, which supports ECMAScript regex syntax including lookaheads, lookbehinds, named groups, and Unicode property escapes.
Can I test regex replacements?▼
Yes! The replace tab lets you test find-and-replace operations with capture group references ($1, $2, etc.). See the replacement result update in real-time as you modify the pattern or replacement string.
Is there a regex cheatsheet?▼
Yes, a quick reference sidebar displays common regex tokens, quantifiers, character classes, anchors, and groups with descriptions and examples. Perfect for learning or quick lookups while building patterns.